Downloaded 51 times
![1818
public class ProductsController : ApiController
{
private readonly IMediator mediator;
public ProductsController(IMediator mediator)
{
this.mediator = mediator;
}
[HttpGet]
public IEnumerable<Product> GetProducts(GetProductsQuery query)
{
return this.mediator.Send(query);
}
[HttpPut]
public void ChangeProductFieldValue(ChangeProductFieldValueCommand command)
{
this.mediator.Send(command);
}
}
Splitting to objects](https://image.slidesharecdn.com/cqrsin4steps-long-desktop-dgeka5e-180408123737/75/CQRS-in-4-steps-18-2048.jpg)
![[오픈소스컨설팅] 서비스 메쉬(Service mesh)](https://cdn.slidesharecdn.com/ss_thumbnails/opensourceconsultingservicemesh-210531074807-thumbnail.jpg?width=640&height=640&fit=bounds)
CQRS in 4 steps
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- 3. 33 CQRS Command Query ResponsibilitySegregation
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- 9. 99 Final state -NopCommerce
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- 11. 1111 Disadvantages of this approach •Enormouscontrollers / services / helpers •Classes are not following SRP •Refactoring is really difficult •Complexity in writing unit tests
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- 13. 1313 JIMMY BOGARD CQRS ISA SIMPLE PATTERN Two objects for command/queries where once there was one https://lostechies.com/jimmybogard/2015/05/05/cqrs-with-mediatr-and-automapper/
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- 15. 1515 UI CONTROLLERS APP Command / queryhandlers Command Handler Command Handler Command Handler Command Handler Query Handler Query Handler Query Handler Query Handler
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- 17. 1717 MediatR Simple, umambitious mediator •Simple mediator implementation in .NET • In-process messaging with no dependencies • Request/response, commands, queries, notifications, events https://github.com/jbogard/MediatR
- 18. 1818 public class ProductsController: ApiController { private readonly IMediator mediator; public ProductsController(IMediator mediator) { this.mediator = mediator; } [HttpGet] public IEnumerable<Product> GetProducts(GetProductsQuery query) { return this.mediator.Send(query); } [HttpPut] public void ChangeProductFieldValue(ChangeProductFieldValueCommand command) { this.mediator.Send(command); } } Splitting to objects
- 19. 1919 public class GetProductsQueryHandler:IRequestHandler<GetProductsQuery, IEnumerable<Product>> { private readonly IProductDatabase _database; // ctx public IEnumerable<Product> Handle(GetProductsQuery query) { var products = this._database .Products .Include(p => p.Category) .Include(p => p.FieldValues) .Include(p => p.FieldValues.Select(fv => fv.Field)); // filter products by command values return products.OrderBy(p => p.CreationDate) .Skip((query.Page - 1) * query.Take).Take(query.Take) .ToList(); } } Query handler
- 20. 2020 public class ChangeProductFieldValueCommandHandler :IRequestHandler<ChangeProductFieldValueCommand> { privateIProductDatabase database; private ICategoryFieldService categoryFieldService; private IProductFieldHelper productFieldHelper; private IFieldValidatorFactory fieldValidatorFactory; //ctx public void Handle(ChangeProductFieldValueCommand command) { this._categoryFieldService.ValidateIfFieldCanBeAssignedToProduct (command.FieldId, command.ProductId); var fieldValidator = this._fieldValidatorFactory(command.FieldId); fieldValidator.Validate(command.FieldValue); // business logic _database.SaveChanges(); } } Command handler
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- 22. 2222 •Better structure ofapplication •Lower entry level •Single responsibility + clean code •Clearly defined target and dependencies •Simplicity of writing unit tests Profits after this step
- 23. 2323 •More difficult thansimple controller- database connection Disadvantages of this step
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- 25. 2525 UI CONTROLLERS APP CQRS in thesimplest form Command Handler Command Handler Command Handler Command Handler Query Handler Query Handler Query Handler Query Handler
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- 29. 2929 CONTROLLERS APP Command Handler Command Handler QueryHandler Query Handler Command Handler Command Handler Query Handler Query Handler X Different data access
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- 33. 3333 SQL Views Materialized AutoMapper ProjectTo Dapper MicroORM EF No tracking OrmLite MicroORM SQLQueries 6 4 5 3 1 2 Plenty of options
- 34. 3434 Profits of usingCQRS Different data access •Ease of experiment •Focus on bottlenecks •No impact on other parts of the system
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- 37. 3737 CONTROLLERS APP Command Handler Command Handler QueryHandler Query Handler Query Handler Query Handler Simple read model
- 38. 3838 PlaceOrder http://udidahan.com/2009/06/14/domain-events-salvation/ OrderPlace d SendEmai l DDD - Domainevents Core Logic Event Side Effect
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- 43. 4343 •Ease of creatingread model •Domain events straightly connected to command handlers •No data loss Profits of using CQRS Simple read model
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- 46. 4646 CONTROLLERS APP Command Handler Command Handler QueryHandler Query Handler Query Handler Query Handler Asynchronous read model
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- 50. 5050 •Database focused onproblem •Non-blockable commands •Designed for scale Profits of using CQRS Asynchronous read model
- 51. 5151 •Distributed system •Eventual consistency •Operationalcomplexity Disadvantages of using CQRS Asynchronous read model
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- 56. 5656http://radblog.pl/CQRS CQRS implementation +MediatR: Jimmy Bogard - CQRS with MediatR and AutoMapper - https://lostechies.com/jimmybogard/2016/10/27/cqrsmediatr-implementation-patterns/ Jimmy Bogard - CQRS/MediatR implementation patterns https://lostechies.com/jimmybogard/2015/05/05/cqrs-with-mediatr-and-automapper/ CQRS implementation: Maciek Aniserowicza - CQRS pragmatycznie - https://kupdf.com/download/maciej-aniserowicz-cqrs-pragmatycznie_597c9425dc0d60997f2bb17f_pdf Future Processing - CQRS Simple Architecture - https://www.future-processing.pl/blog/cqrs-simple-architecture/ Derek Comartin - Fat Controllers CQRS Diet - https://codeopinion.com/fat-controller-cqrs-diet-notifications Radek Maziarka - First step - Split to commands and queries http://radblog.pl/2017/08/19/cqrs-first-step-split-to-commands-and-queries/ More generic about CQRS: Greg Young - CQRS Documencts - https://cqrs.files.wordpress.com/2010/11/cqrs_documents.pdf Greg Young - CQRS and Event Sourcing - https://www.youtube.com/watch?v=JHGkaShoyNs Microsoft - CQRS Journey - https://msdn.microsoft.com/en-us/library/jj554200.aspx Udi Dahan - Clarified CQRS - http://udidahan.com/2009/12/09/clarified-cqrs/ CQRS in Node.js https://medium.com/@domagojk/patterns-for-designing-flexible-architecture-in-node-js-cqrs-es-onion-7eb10bbefe17 Herberto Graca - From CQS to CQRS - https://herbertograca.com/2017/10/19/from-cqs-to-cqrs/ Radek Maziarka - CQRS in 4 steps - http://radblog.pl/2017/09/17/cqrs-in-4-steps-lightning-talk/ CQRS in polish: Bulldog - CQRS i Event Sourcing - https://bulldogjob.pl/articles/122-cqrs-i-event-sourcing-czyli-latwa-droga-do-skalowalnosci-naszych-systemow_ it-consulting - CQRS - http://it-consulting.pl/autoinstalator/wordpress/2012/10/18/cqrs-czyli-kto-co-i-jak-zamawia-i-dostarcza/ Łukasz Szydło - P&A + DDD + CQRS = 00 - https://www.youtube.com/watch?v=yhYFL4ujYqY
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Editor's Notes
- #5 The whole presentation is based on my own experience – my projects, my own decisions, my frameworks.
- #39 And it fits well in CQRS, and not in service model of work, because you exacly know where to send event – at the finish of CH. With services you have different types and you would sometimes send event, sometimes not.
- #40 And it fits well in CQRS, and not in service model of work, because you exacly know where to send event – at the finish of CH. With services you have different types and you would sometimes send event, sometimes not.